This application claims priority of International Application No. PCT/GB99/03093, filed Sep. 16, 1999, entitled A HAND GRIPPING TOOL (published in English), which in turn claims priority of Great Britain Application No. 9821888.6, filed Oct. 7, 1998, and Great Britain Application No. 9907797.6, filed Apr. 7, 1999.
The present invention relates to hand tools for gripping objects and in particular, although not exclusively, to hand tools for gripping and extracting protruding screws, nails and other semi-permanent mechanical fastenings from walls and other surfaces, and to hand tools for holding common tools and accessories, such as blades and screw-driver bits.
During the refurbishment of surfaces, such as walls, it may be necessary or desirable to extract previously installed, now unwanted, semi-permanent mechanical fittings.
Damaged or stubborn mechanical fittings including pins, nails, heavy duty staples, wall plugs, self-tapping screws, studs and other similar obstructions are difficult and potentially dangerous to remove, and occasionally considerable damage occurs to the surrounding wall. Inappropriate extraction techniques can also lead to personal injury.
Known gripping and extraction tools include mole grips, pliers, pincers and claw hammers. Embodiments of the present invention aim to provide hand tools which are more flexible, easier to use, provide a firmer, more secure (and hence safer) grip, enable gripping of a wide range of shapes and sizes of objects, and enable a greater extraction force to be exerted on objects compared with known gripping and extraction tools.
According to the present invention there is provided a hand tool for gripping an object, the hand tool comprising a core member extending along a longitudinal axis of the tool; at least two jaws, moveable relative to the core member so as to be openable and closeable, but constrained in a forward direction substantially parallel with said longitudinal axis, at least a portion of each jaw extending from a first end of the core member generally in said forward direction when the jaws are closed, the respective extending portions each having a respective gripping surface; and a sleeve member arranged to be moveable substantially parallel with the longitudinal axis relative to the core member, the sleeve member having at least one forward facing jaw-engaging surface, the jaws, when open, each presenting a respective reverse facing engaging surface to the at least one jaw-engaging surface of the sleeve member; the sleeve member being progressively moveable in the said forward direction to urge the at least one jaw-engaging surface of the sleeve member against the reverse facing engaging surfaces of the jaws, constraint of the jaws in the said forward direction causing urging of the sleeve member against the jaws to force the jaws to close. The hand tool further comprising two lever pins (11) arranged to extend generally transverse to the longitudinal axis and coaxially from opposite sides of the hand tool at least when the jaws are closed, each lever pin extending from and being integral with a respective one of the jaws.
Preferably the sleeve member is generally cylindrical, extends along the longitudinal axis and is arranged coaxially with the core member such that it is movable to radially surround at least a portion of the core member.
Preferably the core member is generally cylindrical and comprises an external screw thread, and the sleeve member comprises a correspondingly threaded bore extending along the longitudinal axis and arranged to receive and threadably engage the core member such that movement of the sleeve member along the longitudinal axis relative to the core member is effected by rotation of the sleeve member with respect to the core member about the longitudinal axis.
Preferably the screw thread is left-handed. This is particularly advantageous when the hand tool is used for gripping and removing right-hand threaded objects from the surfaces in which they are embedded. The left-hand thread of the core member and sleeve member ensures that the hand tool""s grip is not loosened when it is used to rotate the embedded object in the anti-clockwise direction in an attempt to remove it from the surface. The grip may, as a result of the left-handed thread, tighten as the object resists rotation.
The sleeve member may be generally cylindrical, and may comprise an outer surface adapted to be engaged by a spanner or socket for applying torque to the sleeve member about the longitudinal axis. Thus, a greater gripping force may be applied to the object. The adaptation to the sleeve member may take the form of a pair of diametrically opposed flats, or for example, an axially extending section of the sleeve member may have a generally hexagonal outer cross-section.
Advantageously, the sleeve member may comprise a handle portion adapted to facilitate gripping and rotation of the sleeve member by hand. The handle portion may, for example, take the form of a generally cylindrical portion of increased diameter to enable sufficient torque to be applied to the sleeve member by hand to achieve sufficient grip on the object.
Preferably, the sleeve member is not arranged to fully enclose the core member. Preferably a second end of the core member is arranged to extend through the sleeve member in the reverse direction beyond a first end of the sleeve member when the sleeve member is in contact with the jaws.
The protruding second end of the core member may be adapted to be engaged by a spanner or socket (for example it may be hexagonal in cross-section) and in addition, or alternatively, may be adapted to receive and be engaged by a socket drive. This adaption may take the form of a suitably dimensioned square cross-section orifice extending into the second end of the core member generally along the longitudinal axis.
Thus, substantial relative torque may be applied between the core member and sleeve member to close and lock the jaws onto an object, by use of standard hand tools engaging with suitably adapted surfaces of the hand tool.
Advantageously, the jaws, when forced closed by the sleeve member, are each arranged to extend beyond a second end of the sleeve member in the forward direction. This is particularly advantageous as the sleeve member does not then obscure the hand tool operator""s view of the object to be gripped, and enables the operator to hold and manually close the jaw members on the object before tightening the grip by urging the jaw-engaging surface or surfaces of the sleeve member into contact with the corresponding engaging surfaces of the jaws.
The tool may comprise just two jaws.
Preferably, the gripping surfaces of the jaws are arranged to close generally radially and symmetrically on the longitudinal axis when the jaws are forced to close by the sleeve member.
Thus, the jaws may be adapted to open and expand radially to receive between their gripping surfaces an object inserted generally along the longitudinal axis.
The jaws may be coupled to the core member, forming a generally rotationally symmetrical arrangement around the longitudinal axis.
The jaws may be arranged such that when no object is inserted between their gripping surfaces, the jaws may be closed to bring their gripping surfaces into contact with each other generally on the longitudinal axis.
Preferably, the gripping surfaces of the jaws are adapted to provide a good grip on a wide range of shapes and sizes of objects. For example, each gripping surface may include a respective flat portion arranged to oppose the corresponding flat portion or portions on the or each other jaw, respective teeth arranged to intermesh with corresponding teeth on the or each other jaw, and/or respective teeth arranged to oppose but not intermesh with corresponding teeth on the or each other jaw.
Each gripping surface may in addition, or alternatively, comprise a generally V-shaped groove arranged to extend generally along the longitudinal axis to facilitate gripping of generally cylindrical objects aligned with the longitudinal axis.
Preferably, the or each forward facing jaw-engaging surface of the sleeve member is inclined to face the longitudinal axis such that contact with the corresponding engaging surfaces of the jaws applies a force to the jaws having a component transverse to the longitudinal axis (i.e. a radial component).
Preferably, the sleeve member has a single forward facing jaw-engaging surface which is generally frustoconical and is radially disposed symmetrically about the longitudinal axis.
Preferably, the hand tool has a rotational axis of symmetry co-linear with the longitudinal axis.
Preferably, the jaws are pivotally coupled to the core member, although other coupling arrangements are possible.
Preferably, each jaw comprises a respective pivot pin extending from a side of the jaw, each pivot pin being received in a corresponding respective slot in the core member, each said slot extending in a plane substantially perpendicular to the longitudinal axis, the jaws and core member being adapted to permit rotation of each jaw about its respective pivot pin in a plane substantially parallel to the longitudinal axis and to permit movement of each pivot pin, in its respective slot, transverse to the longitudinal axis. Thus, the jaws may hinge open but are also permitted a degree of purely translational motion relative to the core, namely a translation in a direction transverse to the longitudinal axis.
Advantageously, each jaw may comprise two of the said respective pivot pins, the two pivot pins of each jaw extending coaxially from opposing sides of the jaw, and the core member may comprise at least one further slot, the or each further slot extending in a plane including or parallel to the longitudinal axis and hence perpendicular to the plane of the slots receiving the two pivot pins of a respective one of the jaws, the or each further slot being arranged to accommodate a portion of a respective one of the jaws to permit rotation of the jaw about its pivot pins.
Preferably, the further slot or slots are arranged to engage side surfaces of the accommodated portions of the jaws to contain rotation of the jaws about the longitudinal axis relative to the core. Thus, torque about the longitudinal axis may be transmitted to the jaws by means of the core member.
Advantageously, the hand tool may have two jaws, the respective slots, pivot pins, jaws and core member being arranged to permit parallel separation of the gripping surfaces.
This feature enables the jaws to provide a firm and extended grip on generally cylindrical objects.
Advantageously, the pivot pins may be constrained in their respective slots by the sleeve member at least when the jaws are closed, and the sleeve may be movable in the reverse direction sufficiently to release the pivot pins from their respective slots to enable decoupling of the jaws from the core, and hence enable removal and replacement of jaws from the tool.
Thus, the jaws may be replaceable, and different jaws may be utilised (i.e. coupled to the core member) according to the nature of the object to be gripped and/or extracted.
Advantageously, for each jaw, the respective reverse facing engaging surface is generally inclined at an angle to the respective gripping surface, the angle of inclination being generally the same as that between the jaw-engaging surface or surfaces of the sleeve member and the longitudinal axis.
This feature, when coupled with transverse movement of the jaw pivot pins in their slots with respect to the longitudinal axis, enables a relatively large contact area to be maintained between the sleeve member and each jaw for a range of jaw separations. The rear facing engaging portions of the jaws are thus inclined at the same angle as the jaw-engaging surface of the sleeve member to the longitudinal axis provided that the gripping surfaces are parallel to the longitudinal axis.
Although the jaws may be arranged to present respective reverse facing engaging surfaces to the sleeve only when the jaws are open, it is preferable that these engaging surfaces are presented to the jaw-engaging surfaces of the sleeve even when the jaws are closed to enable tightening of the jaws onto even very small objects.
This may be achieved by employing jaws which taper sufficiently outward (i.e. transverse to the longitudinal axis) in the forward direction from the core member.
Preferably, the hand tool comprises at least one spring arranged to bias the jaws open.
Advantageously, the hand tool may further comprise two lever pins arranged to extend generally radially (transverse to the longitudinal axis) and coaxially from opposite sides of the hand tool, at least when the jaws are closed.
The pins may be used to facilitate the manual application of torque to the sleeve member or core member to close or release the jaws, or may be engaged by a lever pivoting on a fulcrum to pull the hand tool from a surface.
Preferably, each lever pin extends from and is integral with a respective one of the jaws such that when the lever pins are used to pull the hand tool (for example to extract a gripped object from a wall), the grip is not loosened, as might be the case if the pins were located on the sleeve member.
Preferably, the hand tool may be combined with a lever assembly comprising a lever having a first end adapted to engage the lever pins of the hand tool, a second end providing a handle, and fulcrum pins extending transversely and coaxially from a region between the first and second ends, a plate member for positioning against a surface from which an object is to be extracted, and a fulcrum pin support member extending in a direction generally perpendicular to the plate member and providing a support for the fulcrum pins.
The fulcrum pin support member may, advantageously, be adapted to provide an adjustable height support for the fulcrum pin relative to the plate member.